Iranian Foreign Minister Mohammad Javad Zarif on Wednesday said a nuclear deal with Western powers was "within reach" and could open the way to joint action against extremism, as talks continued in Vienna.

"Iran is ready to strike a fair and balanced deal and prepared to open new horizons to address the shared challenges of far greater magnitude," Zarif wrote in a commentary piece in the Financial Times.

"Among these shared threats is the increasingly brutal extremism that is engulfing the heart of the Middle East and even extending into Europe," he added.

Zarif referred specifically to Islamist-inspired killings in France, Kuwait and Tunisia on June 26.

He also condemned Western sanctions against his country, which are intended to thwart Iran's nuclear ambitions, which Tehran insists are peaceful, saying they were "the most indiscriminate imposed on any nation in human history".

"My counterparts have rightfully opted for the negotiating table. But they still need to make the critical choice between an agreement and coercion," said Zarif, who is taking part in the Vienna talks.

In a game of high-stakes diplomatic brinkmanship, global powers readied Wednesday for a late-night push to forge a deal to end a 13-year standoff.

Iran and six world powers on Tuesday effectively gave themselves until Friday to reach a deal by extending a November 2013 interim accord, after missing two target dates in this round of talks now in their 12th day.